A coil apparatus that is installed in the circuits of various AC devices includes a coil component consisting of a coil wound around an annular core.
In order to readily wind the coil around the core, a coil component has been proposed in which a core with an opening formed in a portion thereof is formed, a pre-wound air core coil is inserted through this opening, and thereafter a magnetic or nonmagnetic filler is used to backfill the opening and make the opening into a gap (e.g., see FIG. 10 of Patent Document 1).
In contrast, the applicant has proposed a gapless core in which a core pre-formed in an annular shape is cut at two places and a segment is cut out, the segment is fitted into a cutout part formed in the remaining C-shaped body, and respective end faces are abutted against each other (see Patent Document 2).